DSpace Collection:http://hdl.handle.net/10204/4576
Tue, 03 Mar 2015 20:25:32 GMT2015-03-03T20:25:32ZCrushing damage estimation for pavement with lightly cementitious baseshttp://hdl.handle.net/10204/7752
Title: Crushing damage estimation for pavement with lightly cementitious bases
Authors: De Beer, M; Van Rensburg, Y; Komba, JJ
Abstract: Crushing (or compression) failure and associated surface deformation of lightly cementitious (stabilised) materials used for base/sub-base course layers in pavements has been well established in the South African pavement design practice since the 1990s. Typically, crushing failure starts at the surface of the cementitious base layer, and could extend to 50 mm deep, depending on tyre load/stress conditions. Recently developed crushing damage relationships for 2, 5, 10, 15 and 20 mm level of deformation (“rut”) were proposed for practical application on these pavements. The aim of this paper is the practical application of these relationships for an un-surfaced and surfaced pavement with a typical stabilised (C3 – quality) base layer. Currently there are up to 15 standard pavement designs with cementitious base layers proposed in TRH 4 (1996). This paper demonstrates the impact of four different tyre models (including overloading) used in the mechanistic-empirical design of these pavements. In particular, the importance of adequate surface protection is demonstrated with reference to the vertical tyre contact stresses expected on these cementitious layers. The impact of the findings extends to the use (or not) of C3 - quality bases and associated surfacings on all categories of pavements carrying up to 10 million E80s. This is considered important towards the upgrading of secondary (or alternative) road pavements using cementitious stabilisers in the base layer, especially in the light of the potential future attraction of heavily loaded vehicles - with or without overloading on the tyres.
Description: 33rd Southern African Transport Conference (SATC 2014), CSIR International Convention Centre, Pretoria, South Africa, July 2014Tue, 01 Jul 2014 00:00:00 GMThttp://hdl.handle.net/10204/77522014-07-01T00:00:00ZModelling tyre-road contact stresses in pavement design and analysishttp://hdl.handle.net/10204/7032
Title: Modelling tyre-road contact stresses in pavement design and analysis
Authors: Maina, JW; De Beer, M; Van Rensburg, Y
Abstract: Growing traffic volumes, increasing construction and maintenance costs continually drive for more innovative approaches and methodologies towards sustainable road infrastructure. At the current price levels of around R6000 per metric tonne, bitumen, as a “raw” product, is by far the most costly element in flexible pavements, for example compared to Crushed stone, which is at approximately R170 per metric tonne. Since the asphalt layer or relatively thin bituminous seal acts as the stress barrier between rolling tyres and the road structure it needs to be durable so as to withstand current traffic loading and hence contact stresses, given the environmental forces also acting on it. For road infrastructure to perform as expected, it is important to optimize road pavement design, especially close to the surface of the pavement requiring accurate modelling of tyre-road contact stresses. The aim of this paper is to demonstrate modern ways to idealise tyre-road interaction based on Stress-In-Motion (SIM) results, in particular the way in which numerical analyses are used (and developed) to address non-uniformly distributed tyre contact stresses on the surface of the pavements. A tyre model is demonstrated whereby the SIM measured contact stress distribution is idealised with a multitude of circular and rectangular shapes, mimicking the non-uniform characteristics of the contact stresses inside the tyre contact patch. An example, in terms of pavement layer life and strain energy of distortion, is given highlighting the effects of different tyre-road models on a typical flexible road structure, compared to the traditional circular shape model of a single uniformly distributed contact stress.
Description: The 32nd Southern African Transport Conference, CSIR International Convention Centre, Pretoria, South Africa, 8-11 July 2013. Published by SATC.Mon, 01 Jul 2013 00:00:00 GMThttp://hdl.handle.net/10204/70322013-07-01T00:00:00ZToward using tire-road contact stresses in pavement design and analysishttp://hdl.handle.net/10204/6428
Title: Toward using tire-road contact stresses in pavement design and analysis
Authors: De Beer, M; Maina, JW; Van Rensburg, Y; Greben, JM
Abstract: Optimization of road pavement design, especially towards the surface of the pavement, requires a more rational approach to modeling of truck tire-road contact stresses. Various road surfacing failures are given in this paper as examples, and it is shown that the traditional civil engineering tire model represented by a single uniformly distributed vertical contact stress of circular shape is inadequate to explain this type of surface failure. This paper therefore discusses the direct measurement of threedimensional (3D) tire pavement contact stresses using a flatbed sensor system referred to as the “Stress-In-Motion” (SIM) system. The SIM system (or device) consists of multiple conically shaped steel pins, as well as an array of instrumented sensors based on strain gauge technology. The test surface is textured with skid resistance approaching that of a dry asphalt layer. Full-scale truck tires have been tested since the mid-1990s and experience shows that 3D tire contact stresses are non-uniform and the footprint is often not of circular shape. It was found that especially the vertical shape of contact stress distribution changes, mainly as a function of tire loading. In overloaded/underinflated cases, vertical contact stresses maximize towards the edges of the tire contact patch. Higher inflation pressures at lower loads, on the other hand, result in maximum vertical stresses towards the center portion of the tire contact patch. These differences in shape and magnitude need to be incorporated into modern road pavement design. Four different tire models were used to represent a single tire type in order to demonstrate its effect on road pavement response of a typical South African pavement structure. Only applied vertical stress was used for the analyses. It was found that road surface layer life can reduce by as much as 94 percent as a result of simply using a different tire model on the same pavement structure.
Description: Copyright: 2012 The Tire Society. This is an ABSTRACT ONLY.Mon, 01 Oct 2012 00:00:00 GMThttp://hdl.handle.net/10204/64282012-10-01T00:00:00ZDevelopment of the tyre testerhttp://hdl.handle.net/10204/6305
Title: Development of the tyre tester
Authors: Kuduntwane, P; Du Plessis; Els, S
Abstract: Improved mobility depends on simulating and analysing a vehicle’s performance. Therefore,
accurate and efficient tyre models for off-road vehicles are needed. But to get that, we need a tyre tester for adjustable slip, camber and caster angles for improved tyre
lateral data.
Description: 4th CSIR Biennial Conference: Real problems relevant solutions, CSIR, Pretoria, 9-10 October 2012Mon, 01 Oct 2012 00:00:00 GMThttp://hdl.handle.net/10204/63052012-10-01T00:00:00Z